ABSTRACT
Myeloproliferative neoplasms (MPNs) represent a heterogeneous range of clonal hematopoietic stem cell diseases that can be subdivided into classic and nonclassic myeloproliferative disorders (Table 26.1) [1–13]. Classical myeloproliferative disorders include chronic myeloid leukemia (CML) and three major non-CML categories: polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). Nonclassical myeloproliferative disorders include chronic neutrophilic leukemia (CNL), chronic eosinophilic leukemia, not otherwise specified (CEL, NOS), hypereosinophilic syndrome (HES), systemic mastocytosis (SM), chronic basophilic leukemia, atypical CML, chronic myelomonocytic leukemia (CMML), juvenile myelomonocytic leukemia (JMML), 8p11 myeloproliferative syndrome (EMS), and myeloproliferative disorders, not otherwise classified (which include refractory anemia with ring sideroblasts and thrombocytosis, among others). Diagnostic workup of MPN is presented in Figure 26.1. Classification of MPNs https://www.niso.org/standards/z39-96/ns/oasis-exchange/table">
MPN
Molecular/Cytogenetics Characteristics
Classical
CML
BCR–ABL [t(9;22)]; 100%
PV
JAK2 V617F; ~95%
JAK2 V617F; ~40%–50%
ET
JAK2 exon 12 mutations; ~5%
MPL W515L/K; ~1%
PMF
JAK2 V617F; ~50%
MPL W515L/K; ~5%
Nonclassical
CNL
Normal cytogenetics; ~80%
JAK2 V617F; rare cases
CEL, not otherwise specified (CEL, NOS)
No BCR–ABL fusion; no PDGFRA, PDGFRB, or FGFR1 rearrangement; clonality of eosinophils or increased blasts (6%–19% in the BM) required for diagnosis
Myeloid and lymphoid neoplasms with eosinophilia and abnormalities of PDGFRA, PDGFRB, or FGFR1
FIP1L1–PDGFRA fusion; or t(5;12)(q31–33;p12) or variant translocation, or demonstration of an ETV6–PDGFRB fusion gene (or of the rearrangement of PDGFRB)
HES
No clonal cytogenetic or molecular changes; blasts <5% in the BM; eosinophilia >1.5 × 109/L for ≥6 months
SM
KIT D816V; ~90%
Chronic Basophilic Leukemia
Atypical CML
JAK2 V617F; ~20%
MPN, unclassifiable
JAK2 V617F; ~20%–50%; no BCR–ABL fusion
Algorithm for the diagnosis of classical MPNs. https://s3-euw1-ap-pe-df-pch-content-public-u.s3.eu-west-1.amazonaws.com/9780429170478/da7043d1-f22d-431e-b5ce-d16b7eec9abc/content/fig26_1.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/>